This invention relates to an optical scanner for scanning coded bars by means of a laser beam to read a bar code of the coded bars.
POS (point of sales) system are introduced in many department stores and supermarkets in order to improve the efficiency in management of commodities and checking out operations. In such systems, a bar code reader including an optical scanner is used which scans coded bars attached to a commodity by means of a laser beam, detects diffused signal light from the coded bars by means of a photodetector and converts it into a signal having a form of information suitable for subsequent calculation processing. Such bar code reader is commonly constituted from a laser beam generating source, a laser beam shaping optical system, a scanning optical system, a signal light detecting optical system, a waveform shaping circuit and a bar code demodulating circuit. A laser beam emitted from a He-Ne laser is shaped into a laser beam of a suitable size by the beam shaping optical system, and a scanning pattern for the universal reading is formed with the thus shaped laser beam by the scanning optical system and the laser beam is irradiated upon coded bars with the scanning pattern. Diffused light reflected from the coded bars is condensed by the signal light detecting optical system and the signal light is converted into an electric signal by the photodetector. The electric signal is shaped by the signal waveform shaping circuit and then vonverted into a numerical value by the bar code demodulating circuit, and the numerical value thus obtained is transmitted to a POS terminal.
While various types of optical scanners for use with such bar code readers have been proposed and put into practical use, they can be roughly divided into two types including a type which employs a rotary polygon mirror and the other type which employs a hologram disk. Conventional optical scanners of either of the two types are commonly disadvantageous in that, since a scanning pattern generating mirror device including a plurality of reflecting mirrors must be provided in order to obtain a scanning pattern which is composed of a plurality of scanning lines of various directions, the number of components is increased, and the cost is high, and besides miniaturization of the device cannot be achieved. Further, in order to obtain a long or great beam pattern, the reflecting mirrors must necessarily be large in size, which also makes a cause of rise in cost and an obstacle to miniaturization of the device.